This invention relates to an electrosurgical pencil and in particular to such a pencil where the hot lead through which current is transmitted to the blade is isolated from the blade until that particular pencil has been activated.
It is well known in the prior art to use high frequency current to perform surgical functions. In this type of equipment an electrosurgical generator generates current in a particular wave form upon demand and this current is carried to an electrosurgical pencil having a small blade. The current then is transmitted through the blade to the patient and back to the generator through a ground plate attached to the patient. Since the blade is quite small relative to the ground plate, the energy being transferred to the patient through the blade is concentrated on a small area where the high frequency oscillations cause tissue destruction. Typically such devices have two modes of operation, cutting and coagulation, which require current having different wave forms.
In these devices the current is initiated and interrupted by means of a switching circuit in the generator which is controlled either by a switch in the pencil or by a floor switch. In the former, a switching lead runs from the generator to the pencil, with the switching circuit in the generator being activated to provide current to the hot lead when the switching lead and hot lead are electrically interconnected at the pencil. Thus there are three leads to the pencil; a hot lead which runs from the generator to the blade and two switching leads which run from the generator to the pencil. Located in the pencil is a three-position switch which in one position connects one of the switching leads to the hot lead, thereby providing cutting current to the blade, in a second position connects the other switching lead to the hot lead, thereby providing coagulating current to the blade, and in a third position electrically separates all of the leads from one another thereby providing no current to the blade.
The difficulty with these units lies in the fact that several surgeons often simultaneously use pencils which are connected to a common generator. Since the generator provides current upon activation of the switching circuit, when one pencil is activated current is supplied to all of them. Thus, when one of the pencils is left in a position where the blade comes in contact with the patient, and the other pencil is activated, either intentionally or by accident, the first pencil will cause a burn to occur in the patient. While attempts have been made to design the switching circuit in the generator to provide safeguards which present current from accidentally flowing to the wrong pencil, heretofore no safeguards have been provided in the pencil itself to prevent this from occurring.